No description available.

Thesis (M.S.)--Ohio University, August, 1998. / Title from PDF t.p.

Thesis (Ph.D.)--McMaster University, 2007. / Supervisor: Samir E. Chidiac. Includes bibliographical references.

Thesis (Ph.D.). / Written for the Dept. of Civil Engineering and Applied Mechanics. Title from title page of PDF (viewed 2009/06/10). Includes bibliographical references.

Thesis (MEng) -- Stellenbosch University, 2014. / ENGLISH ABSTRACT: Geopolymer concrete is an alternative construction material that has comparable mechanical properties to that of ordinary Portland cement concrete, consisting of an aluminosilicate and an alkali solution. Fly ash based geopolymer concrete hardens through a process called geopolymerisation. This hardening process requires heat activation of temperatures above ambient. Thus, fly ash based geopolymer concrete will be an inadequate construction material for in-situ casting, as heat curing will be uneconomical. The study investigated fly ash/slag based geopolymer concrete. When slag is added to the matrix, curing at ambient temperatures is possible due to calcium silicate hydrates that form in conjunction with the geopolymeric gel. The main goal of the study is to obtain a better understanding of the mechanical properties of geopolymer concrete, cured at ambient temperatures. A significant number of mix variations were carried out to investigate the influence that the various parameters, present in the matrix, have on the compressive strength of fly ash/slag based geopolymer concrete. Promising results were found, as strengths as high as 72 MPa were obtained. The sodium hydroxide solution, the slag content and the amount of additional water in the matrix had the biggest influence on the compressive strength of the fly ash/slag based geopolymer concrete. The modulus of the elasticity of fly ash/slag based geopolymer concrete did not yield promising results as the majority of the specimens, regardless of the compressive strength, yielded a stiffness of less than 20 GPa. This is problematic from a structural point of view as this will result in large deflections of elements. The sodium hydroxide solution had the most significant influence on the elastic modulus of the geopolymer concrete. Steel and polypropylene fibres were added to a high- and low strength geopolymer concrete matrix to investigate the ductility improvement. The limit of proportionality mainly depended on the compressive strength of the geopolymer concrete, while the amount of fibres increased the energy absorption of the concrete. A similar strength OPC concrete mix was compared to the low strength geopolymer concrete and it was found that the OPC concrete specimen yielded slightly better flexural behaviour. Fibre pull-out tests were also conducted to investigate the fibre-matrix interface. From the knowledge gained during this study, it can be concluded that the use of fly ash/slag based geopolymer concrete, as an alternative binder material, is still some time away as there are many complications that need to be dealt with, especially the low modulus of elasticity. However, fly ash/slag based geopolymer concrete does have potential if these complications can be addressed. / AFRIKAANSE OPSOMMING: Geopolimeerbeton is ‘n alternatiewe konstruksiemateriaal wat vergelykbare meganiese eienskappe met beton waar OPC die binder is, en wat bestaan uit ‘n aluminosilikaat en ‘n alkaliese oplossing. Vliegas-gebaseerde geopolimeerbeton verhard tydens ‘n proses wat geopolimerisasie genoem word. Hierdie verhardingsproses benodig hitte-aktivering van temperature hoër as dié van die onmiddellike omgewing. Gevolglik sal vliegas-gebaseerde geopolimeerbeton ‘n ontoereikende konstruksiemateriaal vir in situ gietvorming wees, aangesien hitte-nabehandeling onekonomies sal wees. Die studie het vliegas/slagmentgebaseerde geopolimeerbeton ondersoek. Wanneer slagment by die bindmiddel gevoeg word, is nabehandeling by omliggende temperature moontlik as gevolg van kalsiumsilikaathidroksiede wat in verbinding met die geopolimeriese jel vorm. Die hoofdoel van die studie was om ‘n beter begrip te kry van die meganiese eienskappe van geopolimeerbeton, wat nabehandeling by omliggende temperature ontvang het. ‘n Aansienlike aantal meng variasies is uitgevoer om die invloed te ondersoek wat die verskeie parameters, aanwesig in die bindmiddel, op die druksterkte van die vliegas/slagmentgebaseerde geopolimeerbeton het. Belowende resultate is verkry en sterktes van tot so hoog as 72 MPa is opgelewer. Daar is gevind dat die sodiumhidroksiedoplossing, die slagmentinhoud en die hoeveelheid water in die bindmiddel die grootste invloed op die druksterkte van die vliegas/slagmentgebaseerde geopolimeerbeton gehad het. Die styfheid van die vliegas/slagmentgebaseerde geopolimeerbeton het nie belowende resultate opgelewer nie. Die meeste van die monsters, ongeag die druksterkte, het ‘n styfheid van minder as 20 GPa opgelewer. Vanuit ‘n strukturele oogpunt is dit problematies, omdat groot defleksies in elemente sal voorkom. Die sodiumhidroksiedoplossing het die grootste invloed op die styfheid van die vliegas/slagmentgebaseerde geopolimeerbeton gehad. Staal en polipropileenvesels is by ‘n hoë en lae sterke geopolimeer beton gevoeg om die buigbaarheid te ondersoek. Die die maksimum buigbaarheid het hoofsaaklik afgehang van die beton se druksterkte terwyl die hoeveelheid vesels die beton se energie-opname verhoog het. ‘n OPC beton mengsel van soortgelyke sterkte is vergelyk met die lae sterkte geopolimeerbeton en daar is gevind dat die OPC beton ietwat beter buigbaarheid opgelewer het. Veseluittrektoetse is uitgevoer om die veselbindmiddel se skeidingsvlak te ondersoek. Daar kan tot die gevolgtrekking gekom word dat, alhoewel belowende resultate verkry is, daar steeds sommige aspekte is wat ondersoek en verbeter moet word, in besonder die styfheid, voordat geopolimeerbeton as ‘n alternatiewe bindmiddel kan optree. Volgens die kennis opgedoen tydens hierdie studie, kan dit afgelei word dat die gebruik van vliegas/slagmentgebaseerde geopolimeerbeton, as 'n alternatiewe bindmiddel, nog 'n geruime tyd weg is, as gevolg van baie komplikasies wat gehandel moet word, veral die lae elastisiteitsmodulus. Tog het vliegas/slagmentgebaseerde geopolimeerbeton potensiaal as hierdie komplikasies verbeter kan word.

O uso de escória de alto forno como aglomerante alternativo ao cimento portland tem sido objeto de vários estudos no Brasil e no exterior. Além de representar vantagens ao meio ambiente por ser um resíduo, a escória apresenta boas possibilidades de emprego, principalmente pelo baixo custo e por suas vantagens técnicas das quais se destacam a elevada resistência mecânica, a boa durabilidade em meios agressivos, o baixo calor de hidratação. No entanto, o emprego deste material carece de estudos detalhados da retração, muito superior à do cimento portland. Este trabalho teve como objetivo estudar a cinética das retrações autógena e por secagem não restringidas do cimento de escória ativada em função, principalmente, do tipo e teor de ativadores empregados. Para a retração autógena, o corpo-de-prova foi selado com papel alumínio protegido internamente com plástico. As medidas estenderam-se de 6 horas até 112 dias. O fenômeno da retração também foi analisado com base nos resultados dos ensaios de porosimetria, calorimetria, termogravimetria e difração de raios X. Foram empregados como ativadores: silicato de sódio, cal hidratada + gipsita, cal hidratada e hidróxido de sódio. Como referência foi adotado o cimento portland da alta resistência inicial CPV-ARI. De acordo com os resultados obtidos, a ativação da escória com silicato de sódio apresentou retração por secagem e autógena superior à apresentada pelos demais ativadores e pelo cimento portland. A maior parte dessa retração medida ocorre até os 7 dias. A retração por secagem ocorre em dois estágios: o primeiro logo após a desmoldagem e o segundo a partir do início da formação dos produtos hidratados. O início da retração autógena coincide com o segundo estágio da retração por secagem. Com base nos ensaios de microestrutura, são determinantes para a elevada retração do cimento de escória ativada com silicato de sódio: a baixa porosidade, caracterizada pela predominância quase total de mesoporos; o elevado grau de hidratação e natureza dos produtos hidratados, com predominância quase total de silicato cálcio hidratado (C-S-H). Na ativação com cal e com cal mais gipsita, a composição diferente dos produtos hidratados (baixa formação de C-S-H e presença significativa de fases aluminato e sulfoluminato, respectivamente) altera a porosidade e a retração, principalmente a autógena que apresenta valores inferiores à do cimento portland. A ativação com hidróxido sódio é caracterizada pela elevada retração autógena e baixa formação de C-S-H, com presença significativa de fases aluminato. / The use of ground granulated blast furnace slag (BFS) as an alternative binder to portland cement has been the subject of numerous studies in Brazil and other countries. Because BFS is a residue, its use benefits the environment. Furthermore, BFS cement is less costly and shows technical advantages if compared with normal portland cement, namely the higher strength, good durability in aggressive environments, and low heat of hydration. On the other hand, the high shrinkage of BSF cement is often indicated as one of the major limiting aspects for its use. The objective of this research was to study the development of unrestrained autogenous and drying shrinkage of BSF cement as function, mainly, of the chemical activator types and dosages. Autogenous shrinkage was measured in fully aluminum foil and plastic sheet wrapped specimens. Measurements were taken from 6 hours up to 112 days. Shrinkage was also analyzed in conjunction with mercury posorimetry, conduction calorimetry, thermogravimetric analysis and X-ray diffraction tests. Activators used were sodium silicate, hydrated lime + gypsite, hydrated lime and sodium hydroxide. High early strength portland cement was used as reference. The results showed that autogenous and drying shrinkage were larger when BFS was activated with sodium silicate. Most of the shrinkage occurs before 7 days of hydration. Drying shrinkage occurs in two phases: the first phase immediately after demolding, and the second phase concurrently with the formation of the hydrated products. Autogenous shrinkage coincides with the second phase of the drying shrinkage. Based on microstructure analysis, determining factors could be identified that respond for the high shrinkage of sodium silicate activated BFS cement: low porosity, mostly mesopores; high degree of hydration and chemical nature of the hydrated products, essentially calcium silicate hydrate - C-S-H. Activation with hydrated lime and hydrated lime plus dehydrated calcium results low amounts of C-S-H and significant quantities of aluminate and sulphoaluminate phases, respectively. Porosity and shrinkage, mainly autogenous, are lower than that verified for portland cement mixtures. Activation with sodium hydroxide causes high autogenous shrinkage, small amounts of C-S-H and significant quantities of aluminate phases.

Use of alternative raw materials, especially industrial by-products, is necessary for a sustainable cement industry. By replacing clinker with industrial by-products, consumption of natural resources and energy is decreased. Therefore, both economical and environmentally friendly cements are produced. Several industrial by-products such as fly ash, silica fume, and slag, one of the most widely used industrial by-products, can be used to produce standard blended cements. Besides its many advantages, slag cements are reported to have lower early compressive strengths. Therefore, the objective of this study is to investigate the early-strength improvement of slag cements. In the experimental study, in order not to change the cement type, the additives were incorporated within the minor additional constituent ranges, i.e. less than 5%. First, CEM III/A type control cement was prepared by blending clinker (K) and slag (S), which were separately ground in a laboratory type ball mill. Ground limestone (L) of varying fineness, silica fume (F), and sodium hydroxide (N) were prepared to be used as minor additional constituent. The ground clinker, slag, and gypsum, and the additives at various ratios were blended to obtain 15 CEM III/A type slag cements other than the control. Finally, the fresh and the hardened properties of the cements were determined. As a result of this experimental study, it was observed that addition of limestone generally increased the early compressive strength of slag cements. However, silica fume and sodium hydroxide either decreased or did not affect the early compressive strength of the slag cements.

Orientador: Gladis Camarini / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Civil, Arquitetura e Urbanismo / Made available in DSpace on 2018-08-09T18:12:28Z (GMT). No. of bitstreams: 1 DeMilito_JoseAntonio_D.pdf: 60807018 bytes, checksum: d77cec46bea9822138fd4024fad50842 (MD5) Previous issue date: 2007 / Resumo / Resumo: O gesso é um aglomerante que tem sido muito empregado em revestimento de paredes. Apresenta um bom desempenho, é econômico e de fácil aplicação, mas limitado ao uso interno devido a sua sensibilidade à água. Algumas tentativas têm sido realizadas para melhorar a sua utilização em ambientes sujeitos à umidade. Neste sentido, pesquisas avançam na tentativa de empregar diferentes adições como resinas epóxi, polímeros, cimentos, escórias, impermeabilizantes, entre outros. O objetivo desta tese foi avaliar o desempenho das misturas de gesso com cimento Portland de Alto Forno e sílica ativa nos revestimentos internos e externos sujeitos à umidade. Para isso verificaram-se as propriedades macroscópicas das misturas por meio de ensaios físicos, químicos, físico-químicos e também a avaliação microestrutural utilizando a microscopia eletrônica de varredura. As misturas foram aplicadas em revestimentos de painéis de alvenaria de blocos de concreto e observados visualmente por um período de cinco anos. Além da observação visual foi verificada a resistência de aderência das misturas aplicadas internamente e externamente. Dos resultados obtidos observou-se uma possível coexistência entre o gesso e o cimento e que a adição de sílica ativa na mistura reduz a formação de etringita, principalmente nos revestimentos externos, sujeitos à umidade. A adição de cimento Portland melhora na abrasão e perda de massa, mesmo em idades mais avançadas. Assim, devido ao elevado custo de algumas adições, e as dificuldades de trabalhar com outros tipos de adição na obra, a adição de cimento Portland e sílica ativa ao gesso permitem uma melhoria de resistência, obtendo um revestimento de baixo custo e de fácil manuseio. / Abstract / Abstract: Plaster of Paris is a binding material being used in masonry as a plaster finish coat. Despite being economical, having good performance as and ease with wich it is applied in building, its use is limited to indoors. Some attempts has been made to improve its performance in external environment. In that sense, researches advance in the attempt at using several admixtures like epoxy resins, polymers, cements slags, waterproofing materials among other things. The objective of this thesis is to assess the performance of certain mixtures of rendering material containing plaster of Paris, slag cement and condensed silica fume when applied in the internal and external plaster finish coat. The macroscopic properties of the mixtures were analyzed through physical and chemical tests and also in SEM. Mixtures were applied on coatings of brick and mortar and visually inspected within five years. Bond strengths of the mixtures were measured, both in internal and external walls. Results showed compatibility between plaster of Paris and slag cement and that presence of condensed silica fume in the mixture reduced the formation of etringite, especially in the external coatings. The addition of Portland blastfurnace slag cement reduced the abrasion and the loss of mass, even in older ages. Therefore, due to the high cost of some admixtures, and the difficulty in working with other kinds of admixtures in the construction sites, the mentioned additions to the plaster rendering allow a mechanical strength improvement, thus resulting in low cost and good workability of the plaster finish coat. / Doutorado / Edificações / Doutor em Engenharia Civil

O uso de escória de alto forno como aglomerante alternativo ao cimento portland tem sido objeto de vários estudos no Brasil e no exterior. Além de representar vantagens ao meio ambiente por ser um resíduo, a escória apresenta boas possibilidades de emprego, principalmente pelo baixo custo e por suas vantagens técnicas das quais se destacam a elevada resistência mecânica, a boa durabilidade em meios agressivos, o baixo calor de hidratação. No entanto, o emprego deste material carece de estudos detalhados da retração, muito superior à do cimento portland. Este trabalho teve como objetivo estudar a cinética das retrações autógena e por secagem não restringidas do cimento de escória ativada em função, principalmente, do tipo e teor de ativadores empregados. Para a retração autógena, o corpo-de-prova foi selado com papel alumínio protegido internamente com plástico. As medidas estenderam-se de 6 horas até 112 dias. O fenômeno da retração também foi analisado com base nos resultados dos ensaios de porosimetria, calorimetria, termogravimetria e difração de raios X. Foram empregados como ativadores: silicato de sódio, cal hidratada + gipsita, cal hidratada e hidróxido de sódio. Como referência foi adotado o cimento portland da alta resistência inicial CPV-ARI. De acordo com os resultados obtidos, a ativação da escória com silicato de sódio apresentou retração por secagem e autógena superior à apresentada pelos demais ativadores e pelo cimento portland. A maior parte dessa retração medida ocorre até os 7 dias. A retração por secagem ocorre em dois estágios: o primeiro logo após a desmoldagem e o segundo a partir do início da formação dos produtos hidratados. O início da retração autógena coincide com o segundo estágio da retração por secagem. Com base nos ensaios de microestrutura, são determinantes para a elevada retração do cimento de escória ativada com silicato de sódio: a baixa porosidade, caracterizada pela predominância quase total de mesoporos; o elevado grau de hidratação e natureza dos produtos hidratados, com predominância quase total de silicato cálcio hidratado (C-S-H). Na ativação com cal e com cal mais gipsita, a composição diferente dos produtos hidratados (baixa formação de C-S-H e presença significativa de fases aluminato e sulfoluminato, respectivamente) altera a porosidade e a retração, principalmente a autógena que apresenta valores inferiores à do cimento portland. A ativação com hidróxido sódio é caracterizada pela elevada retração autógena e baixa formação de C-S-H, com presença significativa de fases aluminato. / The use of ground granulated blast furnace slag (BFS) as an alternative binder to portland cement has been the subject of numerous studies in Brazil and other countries. Because BFS is a residue, its use benefits the environment. Furthermore, BFS cement is less costly and shows technical advantages if compared with normal portland cement, namely the higher strength, good durability in aggressive environments, and low heat of hydration. On the other hand, the high shrinkage of BSF cement is often indicated as one of the major limiting aspects for its use. The objective of this research was to study the development of unrestrained autogenous and drying shrinkage of BSF cement as function, mainly, of the chemical activator types and dosages. Autogenous shrinkage was measured in fully aluminum foil and plastic sheet wrapped specimens. Measurements were taken from 6 hours up to 112 days. Shrinkage was also analyzed in conjunction with mercury posorimetry, conduction calorimetry, thermogravimetric analysis and X-ray diffraction tests. Activators used were sodium silicate, hydrated lime + gypsite, hydrated lime and sodium hydroxide. High early strength portland cement was used as reference. The results showed that autogenous and drying shrinkage were larger when BFS was activated with sodium silicate. Most of the shrinkage occurs before 7 days of hydration. Drying shrinkage occurs in two phases: the first phase immediately after demolding, and the second phase concurrently with the formation of the hydrated products. Autogenous shrinkage coincides with the second phase of the drying shrinkage. Based on microstructure analysis, determining factors could be identified that respond for the high shrinkage of sodium silicate activated BFS cement: low porosity, mostly mesopores; high degree of hydration and chemical nature of the hydrated products, essentially calcium silicate hydrate - C-S-H. Activation with hydrated lime and hydrated lime plus dehydrated calcium results low amounts of C-S-H and significant quantities of aluminate and sulphoaluminate phases, respectively. Porosity and shrinkage, mainly autogenous, are lower than that verified for portland cement mixtures. Activation with sodium hydroxide causes high autogenous shrinkage, small amounts of C-S-H and significant quantities of aluminate phases.

A presente pesquisa tem como objetivo desenvolver um novo elemento de cobertura, compatível com o meio ambiente: telhas de cimento alternativo reforçado com fibras celulósicas. Para tanto, foram utilizadas matérias-primas consideradas resíduos industriais (cimento de escória de alto-forno e rejeito de polpa de celulose de eucalipto) para obtenção de pastas cimentícias reforçadas. Os compósitos foram produzidos por dispersão prévia das fibras em água, mistura do compósito em argamassadeira convencional, adensamento por vibração, moldagem em fôrmas, seguida de cura úmida. Foram moldadas placas planas de diferentes formulações de matrizes cimentícias, com as matérias-primas alternativas disponíveis. Com base nos melhores resultados dessa fase preliminar, foram produzidas duas séries de telhas tipo romana \"capa canal\". Foram avaliados o desempenho físico-mecânico, os custos de produção e o comportamento térmico das telhas. Os resultados revelaram a potencialidade dos compósitos obtidos na produção de fibrocimentos alternativos, por meio de técnicas simples e de baixo consumo de energia, direcionados à autoconstrução urbana e rural de baixo custo. / The objective of this study was to develop a new roofing material that would be compatible with the environment: roofing tiles made of alternative cement reinforced with cellulose fibers. Industrial waste materials were used as raw materials (blast furnace slag cement and waste eucalyptus cellulose pulp) to obtain reinforced cement pastes. The composites were produced by previously dispersing the fibers in water, mixing the composite in a conventional cement-mixer, compaction by vibration, shaping them in molds, followed by moist curing. Flat sheets were molded using different formulations of cement matrixes with the alternative raw materials avaiable. Based on the best results from this preliminary phase, two series of Roman tiles for roofing were produced. The physical and mechanical performance, the cost of production, and the thermal behavior of the tiles were evaluated. The results revealed the potential of composites made of alternative fiber-cements, using simple techniques and with low energy consumption, in urban and rural areas for low-cost self-construction.